Waterbears revived after three decades in the freezer. Photo: Eye of Science/JudithWesterfield.com

Scientists at at Japan's National Institute of Polar Research retrieved the creatures from a frozen moss sample collected in Antarctica in 1983. The sample had been stored at minus−20 degrees for just over three decades.

Two waterbears were resuscitated. One of them died after 20 days, but the other went on to successfully reproduce with a third specimen hatched from a frozen egg.

It laid 19 eggs, of which 14 hatched successfully.

Found throughout the world, tardigrades can survive extreme pressure, such as deep underwater, and can even live in the vacuum of space for several days.

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When they're frozen, the creatures enter a state called cryptobiosis, in which their metabolic processes shut down, and they show no visible signs of life.

"The present study extends the known length of long-term survival in tardigrade species considerably," said researchers.

The previous survival record for adult tardigrades under frozen conditions was eight years, and a much earlier study had suggested that the upper limit for survival under normal atmospheric oxygen conditions was about 10 years.

"We want to unravel the mechanism for long-term survival by looking into damage to tardigrades' DNA and their ability to repair it," said research lead Megumu Tsujimoto.

National Institute of Polar Research now plans to work on examining damage to the water bear's genes and its recovery functions to achieve a better understanding of its long-term survival mechanism.

Hardy though the tardigrades in this study undoubtedly were, they didn't beat the record for survival in a frozen state: that's currently held by a nematode worm that managed nearly 39 years.